Production of colored photographic images



'. suitable solvents. Such developers are known as Patented M. 12, 1940 PATENT OFFICE JJQZMQ PRODUCTION OF COLORED PHOTOGRAPHIC WAGES Humphrey Desmond Murray, London, England,

assignor, by mesne assignments, to Ilford Limited, Ilford, Essex, D y

England, 'a British com- "No Drawing. Application July 26, 193a, semi- 13 Claims.

The invention relates to the production of colored photographic images.

It is known that whencertain reducing agents are used as photographic developers for silver halide emulsions, in addition to the black silver image formed upon development there is also formed a colored image which becomes apparent if the metallic silver is removed by 'means of color developers". In addition it is known that a colored image may be formed simultaneously with the silver image, even when the developer itself is incapable of giving a colored image, by employing, for example by mixing with the developer, an accessory substance which is known as a "color-former.

So far as I am aware no comprehensive theory I of the process of color development has been published and the selection of suitable color formers is largely empirical. A number of compounds have been describe as suitable for use as color formers, including for example phenols, naphthols, pyrazolones and coumaranone.

According to the present invention colored images are produced by developing a silver halide photographic emulsion with an alkaline developer containing an aromatic amino developing substance and with a color former comprising a coumaranone which has one or more substituent groups in the benzene ring or an ortho hydroxy w halogen aceto phenone in which the benzene ring may be similarly substituted and which will give either 'coumaranone or coumaranones having substituents in the benzene ring. 4

The aromatic amino developing substances em-, ployed are the known aromatic amine developers for example the alkyl substituted para phenylene diamines such as dimethyland diethyl-paraphenylene diamine and their salts.

The effect of the substituent groups in the coumaranone is to increase the depth of the color produced. In general coumaranones substituted with alkyl and alkoxy groups give-an image which has the red color obtainable with coumaranone itself, but the red is more yellow '(i. e. less blue) and on this account alkyl and alkoxy substituted coumarancnes. are particularly suitable for the formation of reds in two-'- color photographic processeszspecific examples ofsuch substituted coumaranon'es are 5-methoxy= coumaranone, 5-methyl-coumaranonc and 6-' methoxy-coumaranone. Coumaranones' having;

a double ring formation, such as 4:5-benz-E In Great Britain'July 30, 1937 (01. -6) coumaranone and fiz'l-benz-coumaranone, and

alsothose having halogen substituents, such as 'I-chlor-couxnaranone and 5-brom-'6:7'-benzcoumaranone, give a bluer color than coumaranone itself, and are more suitable therefore owing to the closer approximation to the minus green for use in a three-color process. The system of numbering adopted above for the coumaranones is thatused in Beilsteins Handbuch as follows:

00 I 4 a s v t The ortho-hydroxy-w-halogen-aceto-phenones mayconveniently be shown by the following general formula:

o o oinx on where X represents a halogen atom. Specific examples of such compounds are ortho-hydroxyu-chloraceto-phenone (which gives coumaranone itself) 5-methoxy-2-hydroxy-w-chloracetophenone', 4-methoxv-2-hydroxy-w-chloraceto phenone, 2-w-bromacetyl-1-naphthol and 4-brom- 2-u-bromacetyl-l-naphthol. Auwers (Annalen, 1914', 405, 282) and Fries (Berlchte, 1910, 43, 215) have shown that such substances are converted into the corresponding coumaranones with the removal of hydrogen halide by such reagents as alcoholic sodium acetate. As these compounds give colors closely resembling those given by the corresponding coumaranones when used in similar circumstances in the color development of photographic silver halide emulsions, it would appear that under the alkaline conditions of development the ortho-hydroiw-w-halogen-acetophenones are converted into the coumaranones which give the colorin the same way as when the coumaranones themselves are employed. An advantage obtained by using the ortho-hydrow-uhalogen-aceto-phenones is that one stagein the camera or behind a photographic n'egati'veimage,

which will give the corresponding coumaranones iii - photographic emulsion with an alkaline developer or it may. be applied to the residual unaltered suver'ssa left when an initial reduced silver image has been dissolved away as in the reversal process of development, or it may be applied to a developed photographic image in metallic silver which has been fixed by the removal of unaltered silver halide by means of suitable solvents and subsequently converted to a developable silver salt by means of suitable known photographic bleaching agents.

Further, the process may be applied when both developing agent and color-former are allowed to act together in solution upon the emulsion or it may be applied when the color-former is present initially in the emulsion and the developing agent alone is applied in solution.

As a specific example of the use of the colorformers in accordance with the present invention two solutions may be prepared as follows:

(a) Diethyl-para-phenylenediamine hydrochloride gram 0.20 Sodium carbonate (crystals).- grams 7.0 Sodium sulphite (crystals) do- 1.5

Water os" 100 (b) Color former-.- gram 0.25 Methyl alcohol ccs 10 The two solutions (a) and (b) are mixed and applied to a photographic emulsion containing a developable or latent image. When development is complete the image is washed and the silver LA process for the production of colored images comprising developing a silver halide photographic emulsion with an alkaline developer containing an aromatic amino developing sub stance and with a color former selected from the roup consisting of coumaranones and benzcoumaranones, containing at least one substituent in the carbocyclic ring taken from the group consisting of lower alkyl, lower alkoxy and halogen radicals.

2. A process for the production of colored images comprising developing a silver halide containing a developing substance selected from the group consisting of alkyl substituted paraphenylenediamines and their salts and with a color former selected from the group consisting of coumaranones and benzcoumaranones, containing at least one substituent in the carbocyclic taken irom the group consisting of lower alkyl, lower alkoxy and halogen radicals.

3. A process for the production of colored images comprising developing. a silver halide photographic emulsion with an alkaline developer containing a developing substance selected from the group consisting of alkyl substituted paraphenylenediamines and their salts and a benzcoumaranone.

4. A process as set forth in claim 3 wherein the benz-coumaranone is a halogenobenzcoumaranone.

5. A. process for the production of colored images comprising developing a silver halide photographic emulsion with analkaline developer containing a developing substance selected from the group consisting of alkyl substituted paraphenylenediamines and their salts and with a color former which is a coumaranone having a halogen substituent in the benzene ring.

6. A process for the production of colored images comprising developing a silver halide photographic emulsion with an alkaline developer containing a developing substance selected from the group consisting of alkyl substituted paraphenylenediamines and their salts and with a,

color former which is a coumaranone having a substituent in the benzene ring selected from the group consisting of alkyl and alkoxy substituents.

l. A developing solution for use in the development of photographic silver halide emulsions to produce colored images comprising an aromatic amino developing substance and a color former selected from the group consisting of coumaranones and benzcoumaranones, containing at least one substituent in the carbocyclic ring taken from the group consisting of lower alkyl,

lower alkoxy and halogen radicals.

8. A developing solution for use in the development of photographic silver halide emulsions to produce colored images, comprising a developer selected from the group consisting of alkyl substituted para-phenylenediamines and their salts and a color former selected from the group consisting of coumaranones and benmoumaranones, containing at least one substituent in the carhocyclic ring taken from the group consisting of lower alkyl, lower alkoxy and halogen radicals.

9. A photographic silver halide emulsion containing a color former selected from the group consisting of coumaranones and benzcoumaranones, containing at least one substituent in the carbocyclic ring taken from the group consisting of lower alkyl, lower alkoxy and halogen radicals.

10. A process which comprises developing a photographic element bearing an exposed emulsion layer with an aromatic amino developing 

